Intaglio printing presses are widely used in security printing for printing security documents, especially banknotes. Prior art intaglio printing presses are for instance disclosed in Swiss Patent No. CH 477 293 A5, European Patent Applications Nos. EP 0 091 709 A1, EP 0 406 157 A1, EP 0 415 881 A2, EP 0 563 007 A1, EP 0 873 866 A1, EP 1 602 483 A1, and International Applications Nos. WO 01/54904 A1, WO 03/047862 A1, WO 2004/026580 A1, WO 2005/118294 A1, WO 2011/077348 A1, WO 2011/077350 A1, WO 2011/077351 A1, all assigned to the instant Applicant.
FIGS. 1 and 2 schematically illustrate a known intaglio printing press with an intaglio printing unit configuration similar to that disclosed in European Patent Application No. EP 0 091 709 A1.
FIG. 1 shows a sheet-fed intaglio printing press 1 comprising, as is usual in the art, a sheet feeder 2 for feeding sheets to be printed, an intaglio printing unit 3 for printing the sheets, and a sheet delivery unit 4 for collecting the freshly-printed sheets. The intaglio printing unit 3 typically includes an impression cylinder 7, a plate cylinder 8 carrying intaglio printing plates (in this example, the plate cylinder 8 is a three-segment cylinder carrying three intaglio printing plates 8a, 8b, 8c FIG. 2), an inking system 9 for inking the surface of the intaglio printing plates 8a, 8b, 8c carried by the plate cylinder 8 and an ink wiping system 10 for wiping the inked surface of the intaglio printing plates 8a, 8b, 8c carried by the plate cylinder 8 prior to printing of the sheets.
The sheets are fed from the sheet feeder 2 onto a feeder table and then onto the impression cylinder 7. The sheets are then carried by the impression cylinder 7 to the printing nip between the impression cylinder 7 and the plate cylinder 8 where intaglio printing is performed. Once printed, the sheets are transferred from the impression cylinder 7 to a sheet transporting system 11 in order to be delivered to the delivery unit 4. The sheet transporting system 11 conventionally comprises an sheet conveyor system with a pair of endless chains driving a plurality of spaced-apart gripper bars for holding a leading edge of the sheets (the freshly-printed side of the sheets being oriented downwards on their way to the delivery unit 4), sheets being transferred in succession from the impression cylinder 7 to a corresponding one of the gripper bars.
During their transport to the sheet delivery unit 4, the freshly printed sheets are preferably inspected by an optical inspection system 5. In the illustrated example, the optical inspection system 5 is advantageously disposed along the path of the sheet transporting system 11, right after the printing unit 3. Such an optical inspection system 5 is already known in the art and does not need to be described in detail. Examples of optical inspection systems adapted for use as optical inspection system 5 in the intaglio printing press of FIG. 1 are for instance described in International Applications Nos. WO 97/36813 A1, WO 97/37329 A1, WO 03/070465 A1 and WO 2011/161656 A1. Such inspection systems are in particular marketed by the Applicant under the product designation NotaSave®.
Before delivery, the printed sheets are preferably transported in front of a drying or curing unit 6 disposed after the inspection system 5 along the transport path of the sheet transporting system 11. Drying or curing could possibly be performed prior to the optical inspection of the sheets.
FIG. 2 is a schematic view of the intaglio printing unit 3 of the intaglio printing press 1 of FIG. 1. As already mentioned, the intaglio printing unit 3 basically includes the impression cylinder 7, the plate cylinder 8 with its intaglio printing plates 8a, 8b, 8c, the inking system 9 and the ink wiping system 10.
The inking system 9 comprises in this example four inking devices, three of which cooperate with a common ink-collecting cylinder or Orlof cylinder 9.5 (here a two-segment cylinder) that contacts the plate cylinder 8. The fourth inking device is disposed so as to directly contact the surface of the plate cylinder 8. It will be understood that the illustrated inking system 9 is accordingly adapted for both indirect and direct inking of the plate cylinder 8. The inking devices cooperating with the ink-collecting cylinder 9.5 each include an ink duct 9.10, 9.20, 9.30 cooperating in this example with a pair of inking rollers 9.11, 9.21 and 9.31, respectively. Each pair of inking rollers 9.11, 9.21, 9.31 in turn inks a corresponding chablon cylinder (also designated as selective inking cylinder) 9.13, 9,23, 9.33, respectively, which is in contact with the ink-collecting cylinder 9.5. As for the fourth inking device, it includes an ink duct 9.40, an additional inking roller 9.44, a pair of inking rollers 9.41 and a chablon cylinder 9.43, this latter cylinder being in contact with the plate cylinder 8. The additional ink roller 9.44 is necessary in this latter case as the fourth inking device 9.4 is used to directly ink the surface of the plate cylinder 8 which rotates in opposite direction as compared to the ink-collecting cylinder 9.5. As is usual in the art, the surface of the chablon cylinders 9.13, 9.23, 9.33 and 9.43 is structured so as to exhibit raised portions corresponding to the areas of the intaglio printing plates 8a, 8b, 8c intended to receive the inks in the corresponding colours supplied by the respective inking devices.
The ink wiping system 10, on the other hand, typically comprises a wiping tank 10.1, a wiping roller assembly 10.2 supported on and partly located in the wiping tank and contacting the plate cylinder 8, cleaning means 10.3 for removing wiped ink residues from the surface of the wiping roller assembly 10.2 using a wiping solution that is sprayed or otherwise applied onto the surface of the wiping roller assembly 10.2, and a drying blade 10.4 contacting the surface of the wiping roller assembly 10.2 for removing wiping solution residues from the surface of the wiping roller assembly 10.2. In the above known solution, as schematically illustrated in FIGS. 1 and 2, the entire wiping tank 10.1 together with the wiping roller assembly 10.2 is movable towards and away from the plate cylinder 8 (reference numeral 10′ designating the ink wiping system 10 in a retracted maintenance position), removal of the wiping roller assembly 10.2 from the wiping tank 10.1 during maintenance operations being performed by means of a crane 12 that can be integrated in the press (as shown in FIGS. 1 and 2) or, alternatively, that is provided as separate handling equipment.
A particularly suitable solution for an ink wiping system comprising a wiping roller assembly is disclosed in International Application No. WO 2007/116353 A1 which is incorporated herein by reference in its entirety.
The most common solution used for wiping excess ink from the surface of an intaglio printing cylinder is, as discussed hereinabove, to use a wiping roller assembly that rotates in the same direction as the intaglio printing cylinder. Such wiping roller assembly typically consists of a cylinder base made commonly of metal and bearing at least one layer of wiping material, preferably a layer of polymer material such as PVC material. The structure and manufacture of such wiping roller assemblies is for instance disclosed in U.S. Pat. Nos. 3,785,286, 3,900,595, 4,054,685 and International Applications Nos. WO 2007/031925 A2, WO 2007/031927 A2, WO 2007/034362 A2 which are incorporated herein by reference.
As mentioned above, such wiping roller assembly is typically supported on and partly located in a wiping tank for rotation against the surface of the intaglio printing cylinder, the surface of the wiping roller assembly being cleaned from wiped ink residues using a wiping solution that is commonly sprayed onto the surface of the wiping roller assembly. It is to be understood that, in operation, the wiping roller assembly is supported in an upper section of the wiping tank so that a lower portion thereof can be sprayed with the wiping solution, used wiping solution being recovered in a lower section of the wiping tank.
With such known solutions, the wiping pressure between the intaglio printing cylinder and the wiping roller assembly is adjusted by playing with the position of the axis of rotation of the wiping roller assembly with respect to the axis of rotation of the intaglio printing cylinder. This is typically achieved by using two adjusting mechanisms acting on the two ends of the wiping roller assembly, such by means of eccentric bearings. Adjustment mechanisms for adjusting the wiping pressure between a wiping roller assembly and an intaglio printing cylinder are for instance disclosed in European Patent Applications Nos. EP 0 475 890 A1, EP 0 526 398 A1, and U.S. Pat. Nos. 2,987,993, 3,762,319. More recently, a solution has been proposed by the present Applicant with a view to allow selective adjustment of the wiping pressure at a plurality of locations along the contact portion between the wiping roller assembly and the intaglio printing cylinder. Such a solution is disclosed in greater detail in pending European patent applications Nos. EP 11166852.1 and EP 11166854.7 of May 20, 2011 both entitled “INK WIPING SYSTEM FOR AN INTAGLIO PRINTING PRESS”.
Maintenance operations of the known ink wiping systems are time-consuming as the wiping roller assembly is a relatively heavy component to manipulate, which typically necessitates the use of a crane to remove the wiping roller assembly from the wiping tank as already mentioned. In addition, the use of a crane necessary implies that the wiping roller assembly is extracted from or lowered onto the wiping tank along a substantially vertical trajectory, which in turn necessitates movement of the entire wiping tank, including the wiping roller assembly, to a retracted maintenance position (as for instance indicated by reference numeral 10′ in FIGS. 1 and 2) away from the intaglio printing cylinder in order to create a sufficient distance between the intaglio printing cylinder and the wiping roller assembly. This substantially complicates the overall construction of the ink wiping system and the coupling thereof to the corresponding wiping solution supply and treatment system. This further requires a robust and stable interlocking mechanism to properly secure the wiping tank onto the machine frame during printing operations, which requirement is exacerbated by the fact that the wiping roller assembly which is supported on the wiping tank is subjected to considerable mechanical constraints during printing operations.
An improved solution is thus required.